Mark 14:71

In this one apostle, Peter, the first and chief in the order of apostles, in whom the Church was figured, both sorts were to be signified, viz. the strong and the weak, because the Church is not without both. (St. Augustine, Serm. xiii. de verb. Do.) --- Again, our Saviour would shew by the example of the chief apostle, that no man ought to presume of himself, when even St. Peter was not secure and immoveable. (St. Augustine, tract. lxvi. in Evan. Joan. and St. Leo, serm. ix. de Pass. Do.)